Conventional syngas/hydrogen production technologies use mainly natural gas, LPG and light naptha as feedstocks. As yet, there is no proven catalyst to produce syngas or hydrogen from heavy liquid hydrocarbon fuels (C10+) due to the presence of a high carbon content, a high aromatic content, and sulfur which play a major role in quickly deactivating the catalyst.
With the increased demand for syngas/hydrogen for hydroprocessing in emerging transportation technologies, the need to produce syngas/hydrogen from other resources than natural gas and LPG becomes evermore important.
While the total worldwide annual production of hydrogen is over ½ trillion m3 per year, the need for even greater quantities of hydrogen is still a major bottleneck, especially with the new legislative requirements and pressure to produce ultra low sulfur fuels, while available oil resources become heavier with higher contents of sulfur and metals.
The need for additional hydrogen in refineries is clearly growing, and will continue to grow at a rapid pace for the foreseeable future.
In addition, hydrogen-based fuel cells for automotive and stationary applications are gaining popularity for a variety of reasons, including their higher efficiencies and lower emissions. Nonetheless, using pure hydrogen as a fuel in automotive and residential applications faces many obstacles and has many limitations. The infrastructure to deliver hydrogen is inadequate, the refueling of gaseous hydrogen can be slow, and the storage of hydrogen is problematic. The alternatives to producing and using hydrogen range from futuristic solar energy based hydrogen generation to more pragmatic hydrocarbon reforming. Use of liquid/gaseous hydrocarbon fuels to generate hydrogen is being thought of as an immediate solution for large scale hydrogen production. Besides economics and ease of reforming, this option is seen as being more practical than utilizing the existing distribution network.
The conversion of hydrocarbon fuels to hydrogen can be carried out by several processes, including hydrocarbon steam reforming (HSR), partial oxidation reforming (POR), and auto thermal reforming (ATR). Hydrocarbon steam reforming involves the reaction of steam with the fuel in the presence of a catalyst to produce hydrogen and CO as given in equations (1) and (2) for methane, CH4, and isooctane, C8H18(2,2,4-trimethylpentane), which is used as a surrogate for gasoline. Since steam reforming is endothermic, some of the fuel must be burned and heat transferred to the reformer via heat exchangers.
The choice of the reaction process to be used for on-board reforming depends on many factors, including the operating characteristics of the application (e.g.) varying power demand, rapid startup, and frequent shutdowns) and the type of fuel cell stack. HSR is heat transfer limited and as such does not respond rapidly to changes in the power demand (i.e., “load following”). When power demand rapidly decreases, the catalyst can overheat, causing sintering, which in turn results in a loss of activity, ATR can overcome the load following limitations of HSR, because the heat required for the endothermic reaction is generated within the catalyst bed, a property that allows for more rapid response to changing power demands and faster startup.
In order to supply the large quantity of heat necessary for steam reforming, auto thermal methods involve the a priori combustion of feedstock before entry into the catalytic reformer; the heated gas is then introduced into the catalyst bed. Therefore, the heat supply is limited by the heat capacity of the reactant gases, and does not achieve essential improvements. More recently, the combustion of a part of the hydrocarbon feed has been carried out using catalytic combustion. However, since catalytic combustion is limited by the maximum catalyst-bed temperature of around 1000-1100° C., the situation is not essentially different from a priori homogenous combustion.
While Inui et al, in U.S. Pat. Nos. 7,700,005, 7,820,140 and 8,008,226, which are incorporated herein by reference, disclose various multi-component catalysts for the thermo-neutral reforming of liquid hydrocarbons for the production of hydrogen-rich gas, and Bittencourt et al. Brazilian application PI 000656-7 A2 disclose steam reforming of fuel using a nickel-type catalyst supported on magnesium aluminate which is alkaline promoted to increase catalyst activity, the catalysts and processes of the present invention represent a distinct improvement over the prior art in avoiding deactivation of the catalysts by sulfur and coke deposition which impairs their efficiency and adds to the cost of thermo-neutral refining.